1. Field of the Invention
The present invention generally relates to a displacement transducer and, more particularly, to a miniature transducer for measuring relative changes in thickness of muscles or the like as myocardium wall thickness.
2. Description of the Prior Art
In medical research, particularly involving animals, it is often necessary to measure changes in muscle thickness such as for example changes in the thickness of the myocardium during a cardiac cycle. To this end two different transducers have been proposed in the prior art. However, both prior art transducers suffer from several very serious disadvantages. Each of the prior art transducers penetrates the entire myocardium and includes one element which is pressed against the endocardium while another element of the transducer is pressed against the epicardium. The insertion of such a transducer can result in traumatizing the animal under study. Also, due to their design they are characterized by low compliance, which in effect loads the myocardium and thereby affects its changes in thickness during a normal cardiac cycle. In addition, their implementation is time consuming and requires highly experienced technicians. Another very significant disadvantage of each prior art transducer is the fact that once implanted in the myocardium of an animal it can only be removed by cutting it out of the myocardium. It cannot be extracted and thereafter implanted in a different location of the myocardium of the same living animal. Another undesirable disadvantage of each prior art transducer is the fact that it can only measure changes in the thickness of the entire myocardium. It cannot be used to measure changes or relative changes of the myocardium thickness as a function of different depths within the myocardium.